The histological developments of the gonad and the associated sex steroid levels were determined in the breeding stocks of Acipenser schrenckii (age classes 1 to 5) maintained under natural temperature regimes (December 4°C; August 26°C). Early sex differentiation was observed in 1-year-old fish, while testosterone (T) and 17b-estradiol (E 2 ) levels ranged from T 1.1 to 3.4 nmol l )1 (average 1.8 nmol l )1 ), and E 2 varied from 24 to 85 pmol l )1 (av. 50.3 pmol l )1 ). Gonadal status of 2-year-old males was in stage II while ovaries were at stage I, exhibiting T levels from 1.2 to 4.4 nmol l )1 (av. 2.2 nmol l )1 ), and E 2 concentrations from 10 to 97 pmol l )1 (av. 38.9 pmol l )1 ). At the age of 3 years, the testes in males were at developmental stage III while the ovaries remained in stage I, with T levels ranging from 1.3 to 21.7 nmol l )1 (av. 9.6 nmol l )1 ), and E 2 concentrations ranging from 17 to 108 pmol l )1 (av. 44.8 pmol l )1 ). At the age of 4 years, testes in males were at developmental stage III while ovaries in females had reached stage II, with T concentrations ranging from 7.3 to 52.6 nmol l )1 (av. 26.3 nmol l )1 ), and E 2 levels between 13 and 86 pmol l )1 (average 55.3 pmmol l )1 ). In 5-year-old fish, the testes reached maturity stage while the ovaries were mostly in stage III, with T values from 5.7 to 44.2 nmol l )1 (av. 13.9 nmol l )1 ), and E 2 concentrations from 21 to 453 pmol l )1 (av. 137.7 pmol l )1 ). Data demonstrated large differences in sex steroid levels among immature Amur sturgeon, and testicular maturation occurred earlier than ovarian maturation.

This study aimed to investigate the effect of zearalenone (ZEA) exposure on follicular development in weaned gilts, and its mechanism based on the silent information regulator 1 (SIRT1)/peroxisome proliferator-activated receptor-γ co-activator 1α (PGC-1α) signaling pathway. Thirty-two healthy female weaned piglets (Landrace × Yorkshire × Duroc) with an average body weight of 12.39 ± 0.24 kg were randomly allotted to a basal diet supplemented with 0, 0.15, 1.5, or 3.0 mg/kg ZEA for a 32-d feeding test. Blood and ovarian samples were obtained at the end of the experiment to determine serum toxin concentrations, ovarian histology, and the expressions of proliferating cell nuclear antigen (PCNA) and SIRT1/PGC-1α signaling pathway-related genes. Results showed that the vulva area, serum concentrations of ZEA, α-zearalenol and β-zearalenol, the thickness of growing follicular layer, and the diameter of the largest growing follicles, as well as the expressions of SIRT1, PGC-1α, estrogen-related receptor α (ERRα), ATP synthase subunit beta (ATP5B) and PCNA, increased linearly (P < 0.05) with dietary ZEA increasing, whereas the thickness of the primordial follicle layer decreased linearly (P < 0.05). Immunohistochemical analysis showed that the immunoreactive substances of SIRT1 and PGC-1α in the ovaries enhanced with the increasing dietary ZEA (P < 0.05). In addition, the thickness of growing follicular layer and the diameter of the largest growing follicle were positively correlated with relative mRNA and protein expressions of SIRT1, PGC-1α, ERRα, ATP5B and PCNA (P < 0.05). However, the thickness of primordial follicle layer was negatively correlated with the mRNA and protein expression of SIRT1, PGC-1α, ERRα, ATP5B and PCNA (P < 0.05). Interestingly, the 1.5 mg/kg ZEA treatment had highly hyperplastic follicles, whereas 3.0 mg/kg ZEA resulted in a large number of follicular atresia, which indicated that low-dose ZEA exposure accelerated follicular proliferation, while high-dose ZEA promoted follicular atresia, although the critical value interval needs further confirmation. Results provide a theoretical basis for finding the therapeutic target of ZEA-induced reproductive disorders in weaned gilts.

This study aims to investigate the effects of zearalenone (ZEA) on the localizations and expressions of follicle stimulating hormone receptor (FSHR), luteinizing hormone receptor (LHR), gonadotropin releasing hormone (GnRH) and gonadotropin releasing hormone receptor (GnRHR) in the ovaries of weaned gilts. Twenty 42-day-old weaned gilts were randomly allocated into two groups, and treated with a control diet and a ZEA-contaminated diet (ZEA 1.04 mg/kg), respectively. After 7-day adjustment, gilts were fed individually for 35 days and euthanized for blood and ovarian samples collection before morning feeding on the 36th day. Serum hormones of E2, PRG, FSH, LH and GnRH were determined using radioimmunoassay kits. The ovaries were collected for relative mRNA and protein expression, and immunohistochemical analysis of FSHR, LHR, GnRH and GnRHR. The results revealed that ZEA exposure significantly increased the final vulva area (p < 0.05), significantly elevated the serum concentrations of estradiol, follicle stimulating hormone and GnRH (p < 0.05), and markedly up-regulated the mRNA and protein expressions of FSHR, LHR, GnRH and GnRHR (p < 0.05). Besides, the results of immunohistochemistry showed that the immunoreactive substances of ovarian FSHR, LHR, GnRH and GnRHR in the gilts fed the ZEA-contaminated diet were stronger than the gilts fed the control diet. Our findings indicated that dietary ZEA (1.04 mg/kg) could cause follicular proliferation by interfering with the localization and expression of FSHR, LHR, GnRH and GnRHR, and then affect the follicular development of weaned gilts.